As is known in the art, nodes in a so-called ring network, e.g., FDDI Dual-Attached-Stations (DAS) and SONET Bidirectional Line Switched Ring, are typically daisy chained together. Each node has a link to the previous node and to the next node. The nodes automatically detect a link break and switch over to an alternate path as shown in FIG. 1. For example, in FDDI and SONET networks, the ring is automatically “wrapped” around the break to restore full connectivity to all the nodes.
When it is desired to add a node to an FDDI ring, for example, an operator intentionally breaks the ring by disconnecting the cables going to a node. The nodes surrounding the break assume that the link was broken by a fault and will “wrap the ring” until the ring is restored. Thus, the system behaves no differently than it would during an actual fault event: the system initiates a conventional protection mechanism and suffers a momentary loss of network connectivity. This is acceptable for some networks, as the addition or removal of a node is expected to be an infrequent event. For a data network like FDDI, the brief downtime while the network goes into protection mode is not problematic. SONET networks are designed to minimize fail-over time, specifying a maximum recovery time, because they can carry thousands of circuits that may be sensitive to even brief outages. However, in certain high-availability data networking environments, zero downtime with zero data loss is desired, even if a node needs scheduled maintenance or other activities that require disconnecting a cable.
It would, therefore, be desirable to overcome the aforesaid and other disadvantages.